Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

MAC address table

In Mac address table, Can switch maintain more than one MAC address to the same Port? How it works? How it updates? How long? When it delete the old one | ex. when topology changes? Imagine Switch1 <-> Router1 (port1 but has 2 sub interfaces have different IP). What is the limitation of storing/maintaining MAC address table in switch?



Re: MAC address table

Yes switch can maintain more than one MACs per port. A simple example is when you connect Switch2 to switch1's fa 0/24 then Switch1's fa 0/24 will mantain MACs of all the devices connected to fa switch 2. Based on this only it will forward the traffic. There is a timer called max-age timer. Switch will purge any MAC entries after this time. Default value for this is 300 sec.

There is a command with which you can tell switch how many MACs it is allowed to learn on that port

Re: MAC address table


Yes multiple MAC addresses are supported on each port. The switch learns the MAC by noting the source address of the packet received on each port and on that basis it builds what we call MAC address table. There is an aging mechanism in place which removes the inactive MAC addresses and allows new ones to be learned as devices are connected and disconnected.

The default aging time is 300 seconds, however if need arises you can change the same by giving the command - 'mac address-table aging time number vlan vlan-id'.

Have a look at the following link-->

Hope this helps!



Please rate all helpful posts!!!